JP2012129200A - Semiconductor film, method for preparing semiconductor film, and electricity storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a semiconductor film including silicon microstructures integrated at high density and a method for preparing the semiconductor film; a semiconductor film including silicon microstructures whose density is controlled and a method for preparing the semiconductor film; and an electricity storage device improved in charge-discharge capacity.SOLUTION: A preparation method is used for forming a semiconductor film with a silicon layer including silicon structures on a substrate having one metal surface. The thickness of a silicide layer formed by reaction between the metal and the silicon is controlled, so that the grain sizes of silicide grains formed at an interface between the silicide layer and the silicon layer are controlled and the shapes of the silicon structures are controlled. The semiconductor film can be applied to an electrode of an electricity storage device.

Description

  The present invention relates to a semiconductor film and a method for manufacturing the semiconductor film. The present invention relates to a power storage device.

  Note that the power storage device refers to all elements and devices having a power storage function.

  In recent years, high-performance power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air batteries have been developed.

  An electrode for a power storage device is manufactured by forming an active material on one surface of a current collector. As the active material, a material capable of storing and releasing ions serving as carriers, such as carbon or silicon, is used. For example, silicon or silicon doped with phosphorus has a larger theoretical capacity than carbon and is superior in terms of increasing the capacity of a power storage device (for example, Patent Document 1).

  On the other hand, minute needle-like structures are known, and due to their external features, they are expected to be applied to power storage devices including ion mobile secondary batteries (such as lithium ion batteries).

  A silicon nanoneedle using a VLS (Vapor-Liquid-Solid) growth method is known as a silicon microneedle structure (see Patent Document 2). Silicon nanoneedles are single crystal needle-like structures obtained from a single crystal substrate. As an example, the tip has a diameter of about 300 nm and a length of about 90 μm.

Japanese Patent Laid-Open No. 2001-210315 JP 2003-246700 A

  By using a needle-like structure as the active material of the power storage device, the surface area can be increased, and therefore, effects such as an increase in charge / discharge capacity and an improvement in charge / discharge characteristics are expected. In addition, when a silicon microstructure is used as a negative electrode active material of a power storage device, the charge / discharge capacity is expected to increase as the density is increased. However, it has been difficult to achieve high density and high integration in the conventional method for producing silicon nanoneedles using the VLS growth method.

The present invention has been made under such a technical background. Therefore, an object of one of the objects is to provide a semiconductor film having a silicon microstructure integrated at high density and a manufacturing method thereof.
Another object of the present invention is to provide a semiconductor film having a silicon microstructure whose density is controlled and a manufacturing method thereof.
Another object of the present invention is to provide a power storage device with improved charge / discharge capacity.

  In order to achieve the above object, the present invention has focused on a silicon microstructure formed on a metal surface. The silicon microstructure is formed by depositing a silicon film on a metal surface by using a deposition method such as LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition).

  As a result of intensive research on the generation mechanism of the silicon structure, the present inventors have found that a concavo-convex shape is generated near the surface of the silicide layer due to the compressive stress caused by volume expansion in the metal silicide reaction. It was found that the grain size of the silicide grains separated from the part and the shape of the silicon structure are closely related.

  Then, the inventors have come up with the invention of a semiconductor film having variously shaped silicon structures formed by controlling the grain size of silicide grains that are the nucleus of the growth of silicon structures.

  For example, when forming a needle-like silicon whisker, a silicide structure is formed only in the vicinity of the surface to produce fine silicide grains, and the silicon structure is formed using the silicide grains as a growth nucleus. When the silicide reaction is caused only in the vicinity of the surface, the compressive stress due to the volume expansion accompanying the silicide reaction is concentrated in the direction of the surface of the silicide layer, the unevenness of the uneven shape on the surface of the silicide layer is severe, and the cycle is shortened. As a result, the silicide grains separated from the protrusions on the surface of the silicide layer are extremely minute, and the silicon structure grown from the minute silicide grains is likely to be a needle-like silicon whisker. A semiconductor film having needle-like silicon whiskers formed by such a method has fine silicide grains in the vicinity of the interface between the silicon layer and the silicide layer. The grain size of the silicide grains is 1 nm or more and less than 50 nm.

  On the other hand, when large silicide grains are formed, the silicide reaction may proceed deeply in the film thickness direction (toward the metal layer). When the silicide reaction proceeds deeply in the film thickness direction (toward the metal layer), the compressive stress generated by the volume expansion accompanying the silicide reaction is relaxed in the film thickness direction. As a result, the undulations of the concavo-convex shape on the surface of the silicide layer become gradual and the period becomes longer, and the grain size of the silicide grains separated from the convex part becomes larger. The shape of the silicon structure grown from the large silicide grains thus obtained tends to be a hemispherical (dome-shaped) silicon structure rather than a needle shape. A semiconductor film having a hemispherical (dome-shaped) silicon structure manufactured by such a method has large silicide grains in the vicinity of the interface between the silicon layer and the silicide layer. The grain size of the silicide grains is 50 nm or more.

  Further, as the metal constituting the metal layer, a metal that reacts with silicon to form silicide is used. Examples of metals that form silicide include titanium (Ti), nickel (Ni), cobalt (Co), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), and chromium. (Cr), molybdenum (Mo), tungsten (W), etc. are mentioned. In particular, it is preferable to use titanium having a relatively small diffusion coefficient with respect to silicon because the controllability of the thickness of the silicide layer can be improved.

  In addition, it can be said that the presence of a large number of silicide grains on the silicide layer means that the surface roughness (roughness) of the silicide layer surface is large. Thereby, the adhesion can be improved by providing an anchor effect between the silicide layer and the silicon layer.

  That is, one embodiment of the present invention includes a silicide layer containing a metal, a silicide grain on the silicide layer, a silicide layer and a silicon layer in contact with the silicide grain, and the silicon layer includes a needle-like silicon structure. The thickness of the silicide layer is 1 nm or more and less than 100 nm, and the grain size of the silicide grains is a semiconductor film of 1 nm or more and less than 50 nm.

  One embodiment of the present invention includes a silicide layer containing a metal, a silicide grain on the silicide layer, a silicide layer and a silicon layer in contact with the silicide grain, and the silicon layer includes a dome-shaped silicon structure. The film thickness of the silicide layer is 100 nm or more, and the grain size of the silicide grains is a semiconductor film of 50 nm or more.

  One embodiment of the present invention includes a first region including any of the semiconductor films described above over the same substrate, a metal layer including the metal, an insulating layer over the metal layer, and the insulating layer. The semiconductor layer includes a second region having a second silicon layer over the layer, and the silicon layer in the first region and the second silicon layer are continuous.

  An insulating layer covering the metal layer is formed, the insulating layer is selectively opened so that the metal layer is exposed, and a silicon layer having a silicon structure can be formed only in the opening. In this manner, by selectively forming the silicon structure, the density of the silicon structure in the substrate surface can be arbitrarily controlled. By using the silicon structure whose density is controlled in this way as the active material of the electrode of the power storage device, the silicon structure is prevented from interfering with each other due to volume expansion at the time of charge and discharge, and destruction due to contact is highly reliable. A power storage device can be obtained.

  In one embodiment of the present invention, in each of the semiconductor films described above, the silicide layer and the silicide grain include titanium.

  Further, according to one embodiment of the present invention, a silicide layer containing the metal is formed on the surface of the metal film, and part of the silicide layer is transformed into silicide grains, and a silicon layer containing a silicon structure is formed on the silicide layer. Form. In addition, a method for manufacturing a semiconductor film, in which the shape of the silicon structure is controlled by the thickness of the silicide layer.

  Further, according to one embodiment of the present invention, a silicide layer containing the metal is formed on the surface of the metal film, and part of the silicide layer is transformed into silicide grains, and a needle-like silicon structure is formed on the silicide layer. A silicon layer is formed. Further, the thickness of the silicide layer is 1 nm or more and less than 100 nm, and the size of the silicide grain is 1 nm or more and less than 50 nm.

  Further, according to one embodiment of the present invention, a silicide layer containing the metal is formed on the surface of the metal film, and part of the silicide layer is transformed into silicide grains, and a dome-shaped silicon structure is formed on the silicide layer. A silicon layer is formed. In addition, a method for manufacturing a semiconductor film in which the thickness of the silicide layer is 100 nm or more and the grain size of the silicide grains is 50 nm or more.

  In addition, according to one embodiment of the present invention, in each method for manufacturing a semiconductor film described above, the silicide layer and the silicide grain include titanium.

  Another embodiment of the present invention is a power storage device including the above semiconductor film.

  By applying the semiconductor film having a microstructure of the present invention to a power storage device, a power storage device with improved charge / discharge capacity can be obtained.

  Note that a semiconductor film in this specification and the like refers to a stacked film including a film having properties as a semiconductor and a film having properties as a semiconductor. For example, a stacked film in which a metal film or an insulating film is stacked over a film having semiconductor properties is referred to as a semiconductor film.

  In addition, in this specification etc., the particle size of a grain is defined as the distance between two points that is the longest for every cross section of the grain.

  In this specification and the like, among the microstructures made of silicon, those showing a needle-like shape (including rod-like and branch-like ones) are referred to as needle-like silicon structures, needle-like silicon whiskers. Or silicon whisker. On the other hand, what shows a dome-like shape (including a hemispherical shape and a columnar shape having a hemispherical tip) is referred to as a dome-shaped silicon structure. These may be collectively referred to as a silicon structure.

  According to the present invention, a semiconductor film having a silicon microstructure integrated at high density and a method for manufacturing the semiconductor film can be provided. Further, a semiconductor film having a silicon microstructure whose density is controlled and a manufacturing method thereof can be provided. In addition, a power storage device with improved charge / discharge capacity can be provided.

10A and 10B illustrate a semiconductor film according to an embodiment. 8A to 8D illustrate a method for manufacturing a semiconductor film according to an embodiment. 8A to 8D illustrate a method for manufacturing a semiconductor film according to an embodiment. 10A and 10B illustrate a semiconductor film according to an embodiment. 8A to 8D illustrate a method for manufacturing a semiconductor film according to an embodiment. 6A and 6B illustrate a power storage device according to an embodiment. The figure explaining the electric bicycle which concerns on embodiment. FIG. 6 illustrates an electric vehicle according to an embodiment. 3 is an SEM observation image of the semiconductor film according to Example 1. 3 is an STEM observation image of the semiconductor film according to Example 1. 4 is an STEM observation image of a semiconductor film according to Example 2. 4 is an electron diffraction image of a semiconductor film according to Example 2. FIG.

  Embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated.

  Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for simplicity in some cases. Therefore, it is not necessarily limited to the scale.

(Embodiment 1)
In this embodiment, a semiconductor film including a silicon structure which is one embodiment of the present invention and a manufacturing method thereof will be described with reference to FIGS.

≪Example of semiconductor film configuration≫
FIG. 1A is a schematic cross-sectional view of a semiconductor film having needle-like silicon whiskers, which is exemplified in this embodiment.

  The semiconductor film which is one embodiment of the present invention is formed over the substrate 101 and includes a silicide layer 103, minute silicide grains 105 on the silicide layer 103, and silicon in contact with and covering the silicide layers 103 and 105. Layer 107. The silicon layer 107 has needle-like silicon whiskers 111 and 113.

  The silicide layer 103 is made of silicide obtained by reacting a metal constituting a metal layer 109 described later with silicon. The silicide grains 105 are also composed of similar constituent elements. The silicide layer 103 and the silicide grain 105 have the same constituent elements, but may have different compositions and crystal structures.

  FIG. 1A shows a cross section along the major axis direction of the needle-shaped silicon whisker 111 and a cross section along a direction substantially perpendicular to the major axis direction of the needle-shaped silicon whisker 113. Note that the boundary between the silicon layer 107 and the silicon whiskers 111 and 113 is not clear and is not clearly shown in the drawing.

  The silicon layer 107 and the needle-like silicon whiskers 111 and 113 have crystallinity. Needle-like silicon whiskers 111 and 113 may have uniaxial orientation in the major axis direction.

  Here, FIG. 1B shows an enlarged view of a region including the silicide grains 105 in the vicinity of the boundary between the silicon layer 107 and the silicide layer 103 surrounded by a broken line in FIG.

  The surface of the silicide layer 103 has an uneven shape, and a large number of silicide grains 105 exist in the vicinity of the surface or in the vicinity of the surface.

  The thickness of the silicide layer 103 is 1 nm or more and less than 100 nm, preferably 1 nm or more and less than 50 nm.

  The shape of the silicide grain 105 is not particularly limited as long as it is granular, and includes a spherical shape, an ellipsoid, and the like. Moreover, the particle size is 1 nm or more and less than 50 nm. Here, in this specification and the like, the grain size of a silicide grain is a distance between two points that is the longest with respect to every cross section of the silicide grain.

  Here, the composition of the silicide layer 103 and the silicide grains 105 will be described. The silicide constituting them does not necessarily have a uniform composition across the silicide layer 103 or the silicide grains 105. In the silicide layer 103, the closer to the interface with the silicon layer 107, the higher the proportion of silicon contained. The composition of the silicide grains 105 is composed of silicide with a high silicon ratio (silicon-rich), similar to the composition of the silicide layer 103 near the interface with the silicon layer 107. On the other hand, in a portion deep in the film thickness direction in the silicide layer 103, the silicide layer 103 is composed of silicide with a low ratio of silicon, and metal that is not silicided may remain depending on manufacturing conditions.

≪Method for manufacturing semiconductor film≫
Next, a method for manufacturing a semiconductor film having needle-like silicon whiskers will be described with reference to FIGS.

  First, the metal layer 109 is formed on the substrate 101.

  As the substrate 101, a substrate that can withstand a processing temperature in a later process is used. For example, a glass substrate, a quartz substrate, a ceramic substrate, a semiconductor substrate, or a substrate made of metal can be used. When used as an electrode of a power storage device, it is preferable to use a substrate made of metal. The substrate 101 may have a foil shape, a plate shape, or a net shape.

  For the metal layer 109, a metal that reacts with silicon to form silicide is used. Examples of metals that form silicide include titanium (Ti), nickel (Ni), cobalt (Co), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), and chromium. (Cr), molybdenum (Mo), tungsten (W), etc. are mentioned. In particular, it is preferable to use titanium having a relatively small diffusion coefficient with respect to silicon because the controllability of the thickness of the silicide layer can be improved. In this embodiment mode, titanium is used as a metal used for the metal layer 109.

  The metal layer 109 can be formed using a printing method, a sol-gel method, a coating method, an inkjet method, a sputtering method, a vapor deposition method, or the like as appropriate.

  The metal layer 109 later reacts with silicon to form a silicide layer. The thickness of the metal layer 109 is appropriately set so that the thickness of the silicide layer after the metal layer 109 has reacted with silicon is 1 nm to less than 100 nm, preferably 1 nm to less than 50 nm.

  In this embodiment, a titanium film with a thickness of 10 nm is formed as the metal layer 109 by a sputtering method (see FIG. 2A).

  Subsequently, silicon is deposited so that a metal element constituting the metal layer 109 reacts with silicon to form a silicide layer. As the film formation method, various deposition methods such as an LPCVD method and a PECVD method can be used as appropriate. For example, when the PECVD method is used, the metal element constituting the metal layer 109 reacts with silicon using an RF power supply frequency in the range of 13.56 MHz to 2.45 GHz so that a desired silicide film thickness is formed. The substrate temperature, pressure, gas flow rate, RF power supply power and the like may be adjusted as appropriate.

  In this embodiment mode, silicon is formed using an LPCVD method. The film formation may be performed by supplying a source gas containing a deposition gas containing silicon and at a temperature higher than 500 ° C. and lower than a temperature that the apparatus and the substrate 101 can withstand, preferably 580 ° C. or higher and lower than 650 ° C. The pressure is not less than the lower limit (for example, not less than 5 Pa) and not more than 1000 Pa, preferably not less than 5 Pa and not more than 200 Pa, by allowing the raw material gas to flow.

Examples of the deposition gas containing silicon include silicon hydride gas, silicon fluoride gas, and silicon chloride gas. Typically, SiH ₄ , Si ₂ H ₆ , SiF ₄ , SiCl ₄ , Si ₂ Cl _{6, and the} like. There is. Note that hydrogen may be introduced into the gas. Further, a rare gas such as helium, neon, argon, xenon, or nitrogen may be mixed with the source gas.

  Further, a gas containing an impurity element imparting one conductivity type to silicon such as phosphorus or boron may be mixed with the source gas. By using silicon to which an impurity element imparting one conductivity type such as phosphorus or boron is added for the silicon layer and the silicon structure, the conductivity can be increased. By using this for the active material of the electrode of the power storage device, the charge / discharge characteristics can be further enhanced.

Note that the temperature, pressure, time, gas flow rate, and the like of the LPCVD method are adjusted as appropriate so that the metal forming the metal layer 109 reacts with silicon to form silicide. In this embodiment mode, film formation is performed using a mixed gas of SiH ₄ and nitrogen as a source gas and holding at 20 Pa and 600 ° C. for 1 hour.

  By the LPCVD method, the metal constituting the metal layer 109 and silicon react to form the silicide layer 103. In the present embodiment, the metal constituting the metal layer 109 undergoes a silicidation reaction across almost the entire layer to form the silicide layer 103. Here, depending on conditions, a non-silicided metal layer may remain under the silicide layer 103.

  An uneven shape is formed on the surface of the silicide layer 103, and a plurality of silicide grains 105 are formed in the vicinity of the surface of the silicide layer 103 or close to the surface. The grain size of the silicide grains 105 increases with the thickness of the silicide layer 103, but is 1 nm or more and less than 100 nm, preferably 1 nm or more and less than 50 nm.

  When the metal constituting the metal layer 109 is silicided, compressive stress is generated due to its volume expansion. This compressive stress is concentrated toward the surface of the silicide layer without being able to be relaxed in the film thickness direction when the thickness of the formed silicide is thin. As a result, the unevenness on the surface of the silicide layer becomes severe. Therefore, the silicide grains separated from the protrusions on the surface of the silicide layer can be made extremely minute.

Further, the number of silicide grains formed in this way can be about 10 to several hundred per 1 μm ² . Considering that the cross-sectional area of the acicular silicon whisker is about several hundred nm ^{2 to} several hundred μm ² , although depending on the silicon film formation conditions, the silicide grains serving as the growth nuclei of the acicular silicon whisker are It is very densely distributed. Therefore, it becomes possible to form needle-like silicon whiskers with extremely high density.

  In addition, a silicon layer 107 and a plurality of needle-shaped silicon whiskers (silicon whiskers 115, 117, and 119) are formed to cover the silicide layer 103 and the plurality of silicide grains 105 (FIG. 2B).

  The acicular silicon whisker grows with the silicide grains 105 as nuclei. As the diameter of the silicide grain 105 is smaller, the shape of the silicon whisker tends to be needle-like. In addition to the needle-like silicon whisker, the surface of the silicon layer 107 may be formed with convex portions.

  Through the above steps, a semiconductor film having acicular silicon whiskers can be formed on the substrate 101 with extremely high density. Further, the semiconductor film formed through such a process has silicide grains 105 in the vicinity of the surface of the silicide layer 103 or close to the surface, and the thickness of the silicide layer 103 is 1 nm or more and less than 100 nm, preferably 1 nm or more. It is less than 50 nm, and the grain size of the silicide grains 105 is 1 nm or more and less than 50 nm.

  As described above, according to the manufacturing method of the present invention, a semiconductor film having acicular silicon whiskers can be formed at an extremely high density. In addition, by using such a semiconductor film having extremely high-density needle-like silicon whiskers as an active material of an electrode of a power storage device, a power storage device with improved charge / discharge capacity can be obtained.

<< Modification 1 >>
Next, a semiconductor film having a needle-like silicon whisker structure different from the above and a manufacturing method thereof will be described with reference to FIGS.

  The semiconductor film having needle-like silicon whiskers shown in FIG. 3B has a silicide layer 123 in which the vicinity of the surface of the substrate 121 made of metal is silicided, and is near or close to the surface of the silicide layer 123. A large number of silicide grains 125. Further, a silicon layer 127 having a plurality of needle-like silicon whiskers (silicon whiskers 131, 133, and 135) that covers and contacts the silicide layer 123 and the many silicide grains 125 is provided.

  The structure of the semiconductor film having needle-like silicon whiskers shown in FIG. 3B is different from the above structure in that the vicinity of the surface of the substrate 121 made of metal has a silicide layer 123 that is silicided. Note that the details of the differences from the above will be described here, but detailed descriptions of the common parts are omitted.

  For the substrate 121, a metal that reacts with silicon to form silicide is used. As a metal for forming silicide, the same metal as that used for the metal layer 109 can be used. In this embodiment mode, titanium is used as a metal constituting the substrate 121.

  In the vicinity of the surface of the substrate 121, a silicide layer 123 in which a metal constituting the substrate 121 and silicon are reacted is formed. The thickness of the silicide layer 123 is 1 nm or more and less than 100 nm, preferably 1 nm or more and less than 50 nm, like the silicide layer 103.

  In addition, the silicide layer 123 has a large number of silicide grains 125 in the vicinity of or in the vicinity of the surface of the silicide layer 123. The silicide grains 125 have the same characteristics as the silicide grains 105.

  Note that the composition of the silicide layer 123 and the silicide grain 125 does not necessarily have a uniform composition as described above, and the closer to the interface with the silicon layer 127, the more rich the silicon composition.

  As a manufacturing method, first, a substrate 121 made of metal is prepared (FIG. 3A). Subsequently, silicon may be directly deposited on the substrate 121. At that time, the film formation is performed under such a condition that the thickness of the silicide layer 123 formed on the surface of the substrate 121 is 1 nm or more and less than 100 nm, preferably 1 nm or more and less than 50 nm, as shown in FIG. Such a silicon layer 127 and a plurality of needle-like silicon whiskers (silicon whiskers 131, 133, and 135) can be formed.

<< Modification 2 >>
In contrast to the needle-shaped silicon whisker manufacturing method described above, the silicide layer formed by reacting with silicon is formed to have a thickness of 100 nm or more, and the silicide grain size is set to 50 nm or more. Thus, a silicon microstructure having a shape different from that of the needle-like silicon whisker can be manufactured.

  FIG. 4 is a schematic cross-sectional view of a semiconductor film having a silicon structure formed over a substrate 101, which is one embodiment of the present invention.

  A semiconductor film having a dome-shaped silicon structure illustrated in FIG. 4 includes a metal layer 149 and a silicide layer 143 in which the vicinity of the surface of the metal layer 149 is silicided on the substrate 101, and the vicinity of the surface of the silicide layer 143. Alternatively, a large number of silicide grains 145 are provided close to the surface. Further, a silicon layer 147 having a plurality of dome-like silicon structures (silicon structures 151 to 154) covering and covering the silicide layer 143 and the many silicide grains 145 is provided.

  The plurality of silicon structures 151 to 154 are micro structures having a dome shape (including a hemispherical shape, including a hemispherical columnar shape at the tip) and having crystallinity. Similar to the needle-shaped silicon whisker, the silicon structures 151 to 154 do not have a clear boundary with the silicon layer 147.

  The silicide layer 143 has a film thickness of 100 nm or more, and has a large number of silicide grains 145 near or close to the surface thereof. The particle diameter of the silicide grains 145 is 50 nm or more.

  Note that the composition of the silicide layer 143 and the silicide grains 145 does not necessarily have a uniform composition as described above, and the closer to the interface with the silicon layer 147, the more rich the silicon composition.

  FIG. 4 shows a metal layer 149 that remains between the substrate 101 and the silicide layer 143 without reacting with silicon. The metal layer 149 may be a silicide layer 143 depending on the film thickness before the silicon film formation process, the silicon film formation conditions, and the like.

  In order to form the silicon structures 151 to 154 having such a dome shape, in the step shown in Embodiment Mode 1, first, the thickness of the metal layer formed on the substrate is changed to silicide after the silicide reaction. Film formation is performed with a film thickness of 100 nm or more. After that, the silicon structures 151 to 154 can be formed by forming the silicon layer 147 so that the thickness of the silicide layer is 100 nm or more.

  When the silicide reaction proceeds deeply in the film thickness direction (toward the metal layer) during the film formation of silicon, the compressive stress caused by volume expansion is relaxed in the film thickness direction. As a result, the undulations of the concavo-convex shape on the surface of the silicide layer become gentle, and the grain size of the silicide grains separated from the convex portion becomes large. The shape of the silicon structure grown starting from large silicide grains tends to be a dome shape (hemisphere) instead of a needle shape. A semiconductor film having a dome-shaped (hemispherical) silicon structure manufactured by such a method has large silicide grains in the vicinity of the interface between the silicon layer and the silicide layer. The grain size of the silicide grains is 50 nm or more.

  As in the first modification, a dome-shaped silicon structure can be formed on a substrate made of a metal that forms silicide.

  A semiconductor film having such a dome-shaped silicon structure can be a semiconductor film having a larger surface area than a normal silicon film. In addition, since the height in the film thickness direction is lower than that of needle-shaped silicon whiskers, even when this is used, for example, as an active material of an electrode of a power storage device, the distance between the electrode and the separator can be reduced. A power storage device that is thin and has improved charge / discharge characteristics can be obtained.

  Note that this embodiment can be implemented in combination with any of the other embodiments and examples in this specification as appropriate.

(Embodiment 2)
As described in Embodiment 1, when a method for manufacturing a semiconductor film having acicular silicon whiskers according to one embodiment of the present invention is used, acicular silicon whiskers can be formed with extremely high density. However, when such a needle-shaped silicon whisker formed with a very high density is used as an active material of an electrode of a power storage device, a problem may occur. For example, in the case of a lithium ion power storage device, the active material undergoes volume expansion when lithium ions are taken into the active material during charging and discharging. When the needle-shaped silicon whisker formed at an extremely high density, which is one embodiment of the present invention, is used as an active material, there is a risk that the needle-shaped silicon whisker interferes with each other due to the volume expansion and is broken. .
Therefore, in this embodiment, a semiconductor film having needle-shaped silicon whiskers with controlled density and a manufacturing method thereof will be described.

  FIG. 5C is a schematic cross-sectional view of a semiconductor film having selectively formed needle-like silicon whiskers, which is exemplified in this embodiment.

  The semiconductor film exemplified in this embodiment includes a metal layer 171 over the substrate 101, and an insulating layer 175 in contact with the metal layer 171 and having an opening. The opening of the insulating layer 175 has a silicide layer 163 made of silicide in which a metal element constituting the metal layer 171 reacts with silicon, and has a large number of silicides near or near the surface of the silicide layer 163. Having grains 165; Further, a silicon layer 167 having a plurality of needle-like silicon whiskers 177 and 178 covering and covering the insulating layer 175 and the silicide layer 163 and the silicide grains 165 is provided. The silicon whiskers 177 and 178 are formed so as to overlap with the opening of the insulating layer 175 and the silicide layer 163, and no silicon whisker is formed in a region overlapping the insulating layer 175 of the silicon layer 167.

  As the substrate 101, the substrate described in Embodiment 1 can be used. Similarly, the metal described in Embodiment 1 can be used as a metal element included in the metal layer 171.

  The silicide layer 163 is made of silicide in which a metal element constituting the metal layer 171 reacts with silicon. Further, a large number of silicide grains 165 are scattered in the vicinity of the surface of the silicide layer 163 or in the vicinity of the surface. The silicide layer 163 and the silicide grains 165 have the same characteristics as those described in the first embodiment. Here, the film thickness of the silicide layer 163 in the region excluding the vicinity of the outer peripheral portion is 1 nm or more and less than 100 nm, and the particle diameter of the silicide grain 165 is 1 nm or more and less than 50 nm.

  Note that as illustrated in FIG. 5C, the silicide layer 163 may have a thick portion at the outer periphery of the opening of the insulating layer 175. This is because the compressive stress in the volume expansion during the silicidation reaction concentrates on the outer periphery of the opening of the insulating layer 175, so that the silicide formed rises upward in this part, or the silicidation reaction is in the film thickness direction. Due to progressing deeply. The silicide layer 163 may also be formed below the insulating layer 175 in the outer peripheral portion of the opening.

  The silicon layer 167 is formed so as to cover the insulating layer 175 and its opening, but the needle-like silicon whiskers 177 and 178 are formed only in the opening of the insulating layer 175. Therefore, by providing the opening of the insulating layer 175 only at the location where the needle-shaped silicon whisker is to be formed, the needle-shaped silicon whisker can be selectively formed. The density can be arbitrarily controlled.

  Next, a method for manufacturing the needle-shaped silicon whisker will be described with reference to FIGS.

  First, the metal layer 169 and the insulating layer 173 are formed over the substrate 101. The metal layer 169 can be formed using a material and a method similar to those described in Embodiment 1.

  The insulating layer 173 includes, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a silicon nitride oxide film, an aluminum oxide film, an aluminum nitride film, an aluminum oxynitride film, an aluminum nitride oxide film, a hafnium oxide film, and a tantalum oxide film. Alternatively, an insulating film that can withstand heat in a later step, such as a gallium oxide film, is used. The insulating layer 173 can be formed by a method used in a normal semiconductor manufacturing process, such as a plasma CVD method or a sputtering method. Note that an organic insulating film can also be used without being limited to the inorganic insulating film as long as it has heat resistance to subsequent heat treatment.

  In this embodiment, a 300 nm thick titanium film is used as the metal layer 169 over the glass substrate, and a 450 nm thick silicon oxynitride film is used as the insulating layer 173, both of which are formed by a sputtering method (FIG. 5 ( A)).

  After that, the insulating layer 173 is selectively etched using a known photolithography method, so that the insulating layer 175 having an opening is formed (FIG. 5B).

  Although the method for forming the opening in the insulating layer 173 is arbitrary, a fine opening pattern can be formed by using a photolithography method. Specifically, the size of the opening and the distance between the adjacent openings can be reduced to a size equivalent to the diameter of the needle-like silicon whisker. Here, when the opening pattern is large, that is, when the size of the opening and the distance between the openings are large, the area of the opening in which the needle-like silicon whiskers are densely packed in the substrate surface and the needle-like silicon whisker. A region where no is formed is formed. When this is used as an active material for an electrode of a power storage device, there is a risk that in a region where needle-like silicon whiskers are dense, there is a risk of mutual interference, contact and breakage due to volume expansion during charge and discharge as described above. . However, by using a fine pattern equivalent to the diameter of the needle-like silicon whisker using a photolithography method, the number of silicon whiskers formed in one opening is reduced, and the distance between the openings is reduced. It is preferable because the distance between the silicon whiskers can be as close as possible so that the silicon whiskers do not interfere with each other, and the density of the needle-like silicon whiskers can be made uniform at an optimum density within the substrate surface.

  Thereafter, a silicon layer 167 and needle-like silicon whiskers 177 and 178 are formed on the insulating layer 175 and the metal layer 169 exposed in the opening of the insulating layer 175. For the silicon film formation, a method similar to that shown in Embodiment Mode 1 can be applied.

  When the silicon layer 167 is formed, in the opening of the insulating layer 175, a silicide layer 163 made of silicide obtained by reacting a metal element constituting the metal layer 169 and silicon, and a number of silicide grains in the vicinity of the surface or in the vicinity of the surface 165 is formed, and an unreacted metal layer 171 remains in the lower layer.

  Since the silicide grains 165 serving as the nucleus of the growth of the needle-like silicon whisker are formed only in the opening of the insulating layer 175, the needle-like silicon whisker is selectively formed only in the region overlapping the opening, A needle-like silicon whisker is not formed in the region having the insulating layer 175.

  As described above, needle-like silicon whiskers can be selectively formed on the substrate. By selectively forming the needle-like silicon whisker in this way, the density of the needle-like silicon whisker in the substrate surface can be appropriately controlled. By using the needle-shaped silicon whisker whose density is controlled as described above as an active material of the electrode of the power storage device, the charge / discharge capacity can be improved and a highly reliable power storage device can be obtained.

  Note that although the substrate 101 is used in this embodiment mode, as shown in the first modification example in the first embodiment, a substrate made of a metal that reacts with silicon to form silicide is used. An insulating layer having an opening may be formed over the substrate, and needle-like silicon whiskers may be selectively formed.

  Alternatively, after forming a metal layer on the substrate and etching the metal layer leaving a desired region for forming the silicon structure, the silicon structure can be selectively formed on the region. By using such a formation method, the process can be simplified.

  In addition, the dome-shaped silicon structure can be selectively formed by combining this embodiment and the method for manufacturing the dome-shaped silicon structure shown in the second modification in the first embodiment.

  Note that this embodiment can be implemented in combination with any of the other embodiments and examples illustrated in this specification as appropriate.

(Embodiment 3)
The silicon structure described in Embodiments 1 and 2 can be used as an electrode of a power storage device. By using at least a pair of electrodes, an electrolyte, and a separator, a secondary battery or a capacitor can be obtained.

In this embodiment, as an example of the above power storage device, one of a pair of electrodes is formed using the silicon structure described in Embodiment 1 and Embodiment 2, and the other is replaced with a lithium-containing metal oxide such as LiCoO _2. A lithium ion secondary battery using such a material and a manufacturing method thereof will be described with reference to FIGS.

  6A is a plan view of the power storage device 951, and FIG. 6B is a cross-sectional view taken along dashed-dotted line AB in FIG. 6A.

  A power storage device 951 illustrated in FIG. 6A includes a power storage cell 955 inside an exterior member 953. In addition, terminal portions 957 and 959 connected to the storage cell 955 are provided. As the exterior member 953, a laminate film, a polymer film, a metal film, a metal case, a plastic case, or the like can be used.

  As illustrated in FIG. 6B, the power storage device 951 includes a negative electrode 963, a positive electrode 965, a separator 967 provided between the negative electrode 963 and the positive electrode 965, and an electrolyte 969 filled in the exterior member 953. The Here, as illustrated in the drawing, a structure including the negative electrode 963, the positive electrode 965, and the separator 967 is a single storage cell 955.

  The negative electrode 963 includes a negative electrode current collector 971 and a negative electrode active material layer 973. As the negative electrode, a substrate made of the metal described in any of Embodiments 1 and 2 can be used for the electrode.

  As the negative electrode active material layer 973, an active material layer including a semiconductor film having the silicon structure described in Embodiments 1 and 2 can be used. The silicon structure layer may be predoped with lithium. Further, in the LPCVD apparatus, the negative electrode active material layer 973 formed of a crystalline silicon layer is formed while holding the negative electrode current collector 971 with a frame-shaped susceptor, so that the negative electrode active material 971 is simultaneously formed on both surfaces of the negative electrode current collector 971. Since the material layer 973 can be formed, the number of steps can be reduced.

  The positive electrode 965 includes a positive electrode current collector 975 and a positive electrode active material layer 977.

  The negative electrode active material layer 973 is formed on one or both surfaces of the negative electrode current collector 971. The positive electrode active material layer 977 is formed on both surfaces of the positive electrode current collector 975.

  Further, the negative electrode current collector 971 is connected to the terminal portion 959. In addition, the positive electrode current collector 975 is connected to the terminal portion 957. A part of each of the terminal portion 957 and the terminal portion 959 is led out of the exterior member 953.

  Note that in this embodiment, a thin pouched power storage device is shown as the power storage device 951; however, various shapes of power storage devices such as a button-type power storage device, a cylindrical power storage device, and a rectangular power storage device can be used. it can. In this embodiment mode, a structure in which the positive electrode, the negative electrode, and the separator are stacked is shown; however, a structure in which the positive electrode, the negative electrode, and the separator are wound may be used.

  As the positive electrode current collector 975, aluminum, stainless steel, or the like is used. The positive electrode current collector 975 can have a foil shape, a plate shape, a net shape, or the like as appropriate.

The positive electrode active material layer 977 includes LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMn ₂ PO ₄ , V ₂ O ₅ , Cr ₂ O ₅ , MnO ₂ , and others. A lithium compound can be used as a material. Note that in the case where the carrier ion is an alkali metal ion or alkaline earth metal ion other than lithium, the positive electrode active material layer 977 can be an alkali metal (for example, sodium or potassium), alkaline earth instead of lithium in the lithium compound. Similar metals (for example, calcium, strontium, barium, etc.), beryllium, and magnesium can also be used.

As a solute of the electrolyte 969, a material that can transport lithium ions that are carrier ions and that stably exist lithium ions is used. Typical examples of the electrolyte solute include lithium salts such as LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , and Li (C ₂ F ₅ SO ₂ ) ₂ N. When the carrier ion is an alkali metal ion or alkaline earth metal ion other than lithium, an alkaline earth salt such as a sodium salt or potassium salt, a calcium salt, a strontium salt, or a barium salt is used as the solute of the electrolyte 969. Metal salts, beryllium salts, magnesium salts and the like can be used as appropriate.

  As a solvent for the electrolyte 969, a material that can transfer lithium ions is used. As a solvent for the electrolyte 969, an aprotic organic solvent is preferable. Typical examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran and the like, and one or more of these can be used. In addition, the use of a polymer material that is gelled as a solvent for the electrolyte 969 increases safety including liquid leakage. Further, the power storage device 951 can be reduced in thickness and weight. Typical examples of the polymer material to be gelated include silicon gel, acrylic gel, acrylonitrile gel, polyethylene oxide, polypropylene oxide, and fluorine-based polymer.

As the electrolyte 969, a solid electrolyte such as Li ₃ PO ₄ can be used.

  The separator 967 uses an insulating porous body. Typical examples of the separator 967 include cellulose (paper), polyethylene, and polypropylene.

  Lithium ion batteries have a small memory effect, a high energy density, and a large discharge capacity. Also, the operating voltage is high. For these reasons, it is possible to reduce the size and weight. In addition, there is little deterioration due to repeated charging and discharging, long-term use is possible, and cost reduction is possible.

  Next, a capacitor will be described as the power storage device. Typical examples of the capacitor include a double layer capacitor and a lithium ion capacitor.

  In the case of a capacitor, a material that can reversibly occlude or adsorb lithium ions and / or anions may be used instead of the positive electrode active material layer 977 of the secondary battery illustrated in FIG. Typical examples of the material include activated carbon, a conductive polymer, and a polyacene organic semiconductor (PAS).

  Lithium ion capacitors have high charge / discharge efficiency, can be rapidly charged / discharged, and have a long life due to repeated use.

  When the negative electrode including the silicon structure described in Embodiments 1 and 2 is used for the negative electrode 963, a power storage device with high discharge capacity and reduced deterioration of the electrode due to repeated charge and discharge can be manufactured.

  Further, by using the current collector and the active material layer having the silicon structure described in Embodiments 1 and 2 for the negative electrode of the air battery which is one embodiment of the power storage device, the discharge capacity is high, and repeated charge and discharge Thus, a power storage device with reduced electrode deterioration due to the above can be manufactured.

  Note that this embodiment can be implemented in combination with any of the other embodiments and examples illustrated in this specification as appropriate.

(Embodiment 4)
The needle-shaped silicon whisker described in the first embodiment and the second embodiment can be used for the following applications by making use of its shape. For example, it can also be used for a probe (probe), an electron gun, or a MEMS (Micro Electro Mechanical Systems) used in measurement equipment.

  Further, in this embodiment, application modes of the power storage device described in Embodiment 3 are described with reference to FIGS.

  The power storage device described in Embodiment 3 includes a camera such as a digital camera or a video camera, a digital photo frame, a mobile phone (also referred to as a mobile phone or a mobile phone device), a portable game machine, a portable information terminal, an audio playback device, or the like. It can be used for electronic equipment. Moreover, it can be used for electric propulsion vehicles such as electric vehicles, hybrid vehicles, railway electric vehicles, work vehicles, carts, and wheelchairs. Here, an electric bicycle and an electric vehicle will be described as representative examples of the electric propulsion vehicle.

  FIG. 7 is a perspective view of an electric bicycle (also referred to as an electric assist bicycle). The electric bicycle 1001 is installed in the vicinity of a saddle 1002 where a user sits, a pedal 1003, a frame 1004, two wheels 1005, a handle 1006 for steering one of the wheels 1005, a drive unit 1007 attached to the frame 1004, and the handle 1006. A display device 1008 is included.

  The drive unit 1007 includes a motor, a battery, a controller, and the like. The controller detects the battery status (current, voltage, battery temperature, etc.), controls the motor by adjusting the amount of discharge from the battery during travel, and controls the amount of charge during charging. The driving unit 1007 may be provided with a sensor for detecting the force with which the user steps on the pedal 1003, the traveling speed, and the like, and the motor may be controlled in accordance with information from the sensor. 7 shows a configuration in which the drive unit 1007 is attached to the frame 1004, the attachment position of the drive unit 1007 is not limited to this.

  The display device 1008 is provided with a display portion, a switching button, and the like. The remaining battery level and running speed are displayed on the display. The switch button controls the motor and switches the display on the display. Note that FIG. 7 illustrates a configuration in which the display device 1008 is attached to the periphery of the handle 1006; however, the arrangement of the display device 1008 is not limited to this.

  The power storage device described in Embodiment 3 can be used for the battery of the driver 1007. The battery of the driving unit 1007 can be charged by external power supply using plug-in technology or non-contact power feeding. Further, the power storage device described in Embodiment 3 may be used for the display device 1008.

  FIG. 8A is a perspective view of the electric vehicle 1101. FIG. 8B is a perspective view of the electric vehicle 1101 shown in FIG. The electric vehicle 1101 obtains power by passing a current through the motor 1103. The electric vehicle 1101 includes a battery 1105 that supplies electric power for flowing current to the motor 1103, and a power control unit 1107. In FIG. 8, as a means for charging the battery, although not particularly illustrated, a configuration may be adopted in which a separate generator or the like is provided for charging.

  The power storage device described in Embodiment 3 can be used for the battery 1105. The battery 1105 can be charged by external power supply using plug-in technology or non-contact power feeding. When the electric propulsion vehicle is a railway electric vehicle, charging can be performed by supplying power from an overhead wire or a conductive rail.

  Note that this embodiment can be implemented in combination with any of the other embodiments and examples illustrated in this specification as appropriate.

  In this example, a semiconductor film having a needle-like silicon whisker and a semiconductor film having a dome-shaped silicon structure were manufactured by the method described in Embodiment 1, and each semiconductor film was observed. .

  Hereinafter, a sample in which a semiconductor film having needle-shaped silicon whiskers is formed is referred to as sample 1, and a sample in which a semiconductor film having a dome-shaped silicon structure is formed is referred to as sample 2.

  First, a titanium film was formed on a glass substrate by a sputtering method. In Sample 1, the thickness of titanium was 10 nm, and in Sample 2, the thickness of titanium was 300 nm.

Subsequently, a silicon film was formed on both using the LPCVD method. Film formation is performed by flowing a film forming gas in which SiH ₄ and N ₂ are mixed at a mixing ratio of 1: 1 while maintaining the pressure at 20 Pa and a temperature of 600 ° C. for 1 hour to form a silicon structure. Sample 1 and Sample 2 were obtained.

  Subsequently, the sample 1 and the sample 2 were observed by the SEM (Scanning Electron Microscopy) method. FIG. 9A shows the observation result of the sample 1, and FIG. 9B shows the observation result of the sample 2.

  In Sample 1, it was confirmed that needle-like silicon whiskers were formed at a very high density. In Sample 2, it was confirmed that the dome-shaped (hemispherical) silicon structure was formed at an extremely high density.

  Subsequently, a cross-sectional observation in the vicinity of the silicide layer was performed on the sample 1 and the sample 2 by using a STEM (Scanning Transmission Electron Microscopy) method. FIG. 10A shows the observation result of the sample 1 and FIG. 10B shows the observation result of the sample 2.

  In Sample 1, a plurality of silicide grains having an average grain size of about 18 nm were observed on a silicide layer having a thickness of about 11 nm on a glass substrate, and a silicon layer was provided so as to cover these.

  On the other hand, in Sample 2, a plurality of titanium layers having a thickness of about 50 nm on the glass substrate, a titanium silicide layer having a thickness of about 410 nm on the titanium layer, and a plurality of silicide grains having an average particle size of about 64 nm are observed on the titanium silicide layer. A silicon layer was provided so as to cover them. Further, it was confirmed that the titanium silicide layer was divided into two layers having greatly different compositions, and the lower part was composed of silicide having a low silicon concentration and the upper part being silicide having a high silicon concentration.

  Note that this embodiment can be implemented in combination with any of the other embodiments and embodiments described in this specification as appropriate.

  In this example, a dome-shaped silicon structure is formed by the method exemplified in the first embodiment, and the identification of the crystal structure of the silicide layer and the silicide grains in the vicinity of the interface with the silicon layer is performed by an electron diffraction measurement method. I tried using.

First, a 100 nm-thick titanium film was formed on a glass substrate by a sputtering method. Next, a silicon film was formed using the LPCVD method. The film is formed by maintaining a pressure of 20 Pa and a temperature of 600 ° C. for 1 hour while flowing a film forming gas in which SiH ₄ and N ₂ are mixed at a mixing ratio of 1: 1. Sample 3 in which an object was formed was obtained.

  Subsequently, a cross-sectional observation in the vicinity of the silicide layer was performed on the sample 3 using the STEM method. FIG. 11 shows a cross-sectional observation result.

  From the result of cross-sectional observation, it was confirmed that the silicide layer was a polycrystalline layer containing many grains in the vicinity of the interface with the silicon layer. Further, it was confirmed that the silicide layer has a large number of silicide grains.

  Subsequently, diffraction images of the silicide grains and the silicide layer were observed by an electron beam diffraction measurement method, and an attempt was made to identify the crystal structure. The measurement was performed for the region 1 in the silicide grain and the region 2 in the silicide layer shown in FIG.

  FIGS. 12A and 12B show electron diffraction patterns in regions 1 and 2, respectively. The crystal structure was identified from the measured diffraction spot group. 12A and 12B show surface indices corresponding to several diffraction spots.

From the diffraction image shown in FIG. 12 (A), it was confirmed that the crystal structure in region 1 was C54 phase TiSi ₂ , and the diffraction image shown in FIG. 12 (A) was a [130] incident diffraction image. .

On the other hand, from the diffraction image shown in FIG. 12B, it is confirmed that the crystal structure in the region 2 is C49-phase TiSi ₂ and the diffraction image shown in FIG. 12B is a [101] incident diffraction image. It was done.

  From the above results, it was confirmed that the silicide layer in the vicinity of the interface with the silicon layer was composed of silicon-rich crystalline silicide. Similarly, it was found that the silicide grains are composed of silicon-rich crystalline silicide.

  Furthermore, it was confirmed that the titanium silicide constituting the silicide layer and the titanium silicide constituting the silicide grain have different crystal structures.

  Note that this embodiment can be implemented in combination with any of the other embodiments and embodiments described in this specification as appropriate.

101 substrate 103 silicide layer 105 silicide grain 107 silicon layer 109 metal layer 111 silicon whisker 113 silicon whisker 115 silicon whisker 117 silicon whisker 119 silicon whisker 121 substrate 123 silicide layer 125 silicide grain 127 silicon layer 131 silicon whisker 133 silicon whisker 135 silicon whisker 143 Silicide layer 145 Silicide grain 147 Silicon layer 149 Metal layer 151 Silicon structure 152 Silicon structure 153 Silicon structure 154 Silicon structure 163 Silicide layer 165 Silicide grain 167 Silicon layer 169 Metal layer 171 Metal layer 173 Insulating layer 175 Insulating layer 177 Silicon Whisker 178 Silicon whisker 951 Power storage device 953 Exterior member 955 Power storage cell 957 Terminal portion 959 Terminal portion 963 Negative electrode 965 Positive electrode 967 Separator 969 Electrolyte 971 Negative electrode current collector 973 Negative electrode active material layer 975 Positive electrode current collector 977 Positive electrode active material layer 1001 Electric bicycle 1002 Saddle 1003 Pedal 1004 Frame 1005 Wheel 1006 Handle 1007 Drive unit 1008 Display device 1101 Electric vehicle 1103 Motor 1105 Battery 1107 Power control unit

Claims (9)

A silicide layer containing a metal;
Silicide grains on the silicide layer;
The silicide layer, and a silicon layer in contact with the silicide grains,
The silicon layer includes a needle-like silicon structure;
The thickness of the silicide layer is 1 nm or more and less than 100 nm,
The semiconductor film has a silicide grain size of 1 nm or more and less than 50 nm. A silicide layer containing a metal;
Silicide grains on the silicide layer;
The silicide layer, and a silicon layer in contact with the silicide grains,
The silicon layer includes a dome-shaped silicon structure;
The silicide layer has a thickness of 100 nm or more,
The semiconductor film has a silicide grain size of 50 nm or more. On the same substrate
A first region having the semiconductor film according to claim 1 or 2,
A metal layer including the metal, an insulating layer on the metal layer, and a second region having a second silicon layer on the insulating layer,
A semiconductor film in which the silicon layer of the first region and the second silicon layer are continuous. In any one of Claim 1 thru | or 3,
The semiconductor film, wherein the silicide layer and the silicide grains contain titanium. A silicide layer containing the metal is formed on the surface of the metal film, and part of the silicide layer is transformed into a silicide grain,
Forming a silicon layer including a silicon structure on the silicide layer;
A method for manufacturing a semiconductor film, wherein a shape of the silicon structure is controlled by a thickness of the silicide layer. A silicide layer containing the metal is formed on the surface of the metal film, and part of the silicide layer is transformed into a silicide grain,
Forming a silicon layer including a needle-like silicon structure on the silicide layer;
The thickness of the silicide layer is 1 nm or more and less than 100 nm,
A method for manufacturing a semiconductor film, wherein the silicide grains have a diameter of 1 nm or more and less than 50 nm. A silicide layer containing the metal is formed on the surface of the metal film, and part of the silicide layer is transformed into a silicide grain,
Forming a silicon layer including a dome-shaped silicon structure on the silicide layer;
The silicide layer has a thickness of 100 nm or more,
A method for manufacturing a semiconductor film, wherein the silicide grains have a diameter of 50 nm or more. In any one of Claims 5 thru | or 7,
The method for manufacturing a semiconductor film, wherein the silicide layer and the silicide grains contain titanium.   A power storage device comprising the semiconductor film according to claim 1.